BACKGROUND OF THE INVENTION
[0001] This invention pertains in general to resid hydrocracking methods and in particular
to methods for the production and use of hydrogen donor solvents to increase the efficiency
of processes to convert hydrocarbon residua ("resid") feedstocks to lower boiling
hydrocarbon liquid products.
[0002] It is well known that more hydrogen rich and lower boiling point hydrocarbon distillates
can be produced from hydrogen deficient petroleum residua (resid) by thermally cracking
in presence of a hydrogen donor diluent.
U.S. Patent 2,848,530 discloses a process to produce lower boiling liquid hydrocarbons from a higher boiling
hydrogen deficient petroleum oil by heat treatment in the presence of a lower boiling
point and partially hydrogenated aromatic-naphthenic diluent. Thermal tars, coal derived
liquids, and catalytic cycle oils are preferred hydrogen donor diluent precursors.
[0003] U.S. Patent 3,238,118 teaches the use of a gas oil hydrocracker to produce hydrogen donor diluent precursor.
U.S. Patent 4,090,947 teaches the use of a premium coker gas oil as the hydrogen donor precursor.
U.S. Patent 4,292,168 provides guidance on the desired hydrogen donor diluent properties using model compounds,
but does not provide any guidance on commercially viable methods to produce a hydrogen
donor diluent with the required properties.
U.S. Patent 4,363,716 teaches production of the hydrogen donor diluent precursor by contacting a gas oil
stream with a molybdenum on alumina catalyst and hydrogen at 500 psia and 500°C with
a 0.5 hour residence time. One problem with all these processes is that the more aromatic
hydrogen donor precursor is diluted with the less aromatic gas oil product from the
hydrogen donor cracking product.
[0004] Other patents focus on increasing hydrogen donor process efficiency and maximum operable
resid-to-distillates yield.
U.S. Patent 2,873,245 teaches the use of a second thermal cracking stage with catalytic cracking cycle
(or decant) oil as make-up hydrogen donor diluent precursor. In a similar manner,
U.S. Patent 2,953,513 teaches the use of a second thermal cracking stage with a thermal tar hydrogen donor
diluent precursor.
U.S. Patent 4,698,147 teaches the use of high temperature, short residence time operating conditions to
increase the maximum resid conversion.
U.S. Patent 4,002,556 teaches the use of multiple point hydrogen donor diluent addition points to decrease
the hydrogen requirement.
U.S. Patents 6,183,627 and
6,274,003 teach the use of a deasphalter to recover and recycle deasphalted oil to increase
the maximum operable resid conversion to distillates by selectively removing coke
precursors in the asphaltene product stream.
U.S. Patent 6,702,936 further increases the process efficiency by using partial oxidation of the asphaltene
product to produce hydrogen for the hydrogen donor diluent cracking process.
[0005] U.S. Patent 4,640,765 demonstrates that the addition of a hydrogen donor diluent to a batch ebullated bed
hydrocracker increases the rate of residua conversion to distillates. Unfortunately,
the addition of the hydrogen donor diluent also decreases the concentration of the
residual oil in the ebullated bed hydrocracker. In a continuous ebullated hydrocracker,
the adverse dilution effect is much greater than the beneficial effect of the more
rapid resid conversion kinetics. As a result, efforts to increase the ebullated bed
hydrocracker process maximum resid conversion and process efficiency have primarily
focused on methods to selectively remove coke precursors from the reactor (
U.S. Patents 4,427,535;
4,457,830; and
4,411,768) and preventing coke precursors from precipitating in the process equipment (
U.S. Patents 4,521,295 and
4,495,060).
[0006] U.S. Patents 5,980,730 and
6,017,441 introduce the concept of using a solvent deasphalter to remove coke precursors and
recycle hydrotreated deasphalted oil to the ebullated bed resid hydrocracker. However,
this process does not provide a method to control the hydrogen donor precursor properties
required to produce an effective hydrogen donor solvent and recycles undesirable more
paraffinic residual oil species to the ebullated bed resid hydrocracker.
U.S. Patent 5,228,978 teaches using a solvent deasphalting unit to separate the cracked resid product from
an ebullated bed resid hydrocracker into an asphaltene coker feed stream, a resin
stream that is recycled to the ebullated bed resid hydrocracker, and a more paraffinic
residual oil stream that is fed to a conventional catalytic cracking unit.
U.S. Patent 4,686,028 teaches the use of a deasphalter to separate a resid oil feed into asphaltene, resin,
and oil fractions and upgrading the resin fraction by visbreaking or hydrogenation.
[0007] Therefore, there remains a need for a practical means to effectively produce and
use a hydrogen donor solvent in resid hydrocracking processes that has not been met
by the prior processes.
SUMMARY OF INVENTION
[0008] The present invention provides for a method to use a process derived hydrogen donor
solvent to increase the maximum resid conversion and resid conversion rate in an ebullated
bed resid hydrocracker. The hydrogen donor solvent is produced by hydroreforming and
cracking reactions within typically an ebullated bed resid hydrocracker, recovered
as the resin fraction using a solvent deasphalting unit, regenerated in a separate
hydrotreater reactor, and fed to the ebullated bed resid hydrocracker.
[0009] According to the present invention there is provided a method for increasing the
maximum resid conversion and resid conversion rate in a resid hydrocracker upgrader
comprising the steps:
- a) producing a hydrogen donor solvent precursor (i.e. a partially dehydrogenated solvent)
in the resid hydrocracker, wherein the hydrogen donor solvent precursor is produced
by hydroreforming reactions of a hydrogen donor solvent (feed);
- b) directing the hydrogen donor solvent precursor to a solvent deasphalting unit,
wherein a resin stream containing the hydrogen donor solvent precursor is formed;
- c) directing the resin stream to a (separate) resid hydrotreater unit, wherein hydrogen
donor solvent is (re)generated; and
- d) directing the hydrogen donor solvent to the resid hydrocracker upgrader.
[0010] The invention also provides a method as claimed in claim 11.
[0011] Hydrogen donor solvent precursor is typically also produced by the hydrocracking
of the resid feed in the resid hydrocracker upgrader.
[0012] A simplified reaction system may be useful to illustrate the hydrogen donor process
concept and differentiate this invention from the prior art. For simplicity, this
reaction system uses a phenanthrene hydrogen donor diluent precursor to illustrate
the hydrogen donor process. However, this invention advantageously uses a much higher
molecular weight, more complex, and higher boiling point resin hydrogen donor solvent.
The hydrogen donor process typically starts by hydrogenating a hydrogen donor precursor
solvent or diluent at moderate temperature and high pressure in the presence of a
catalyst such as nickel-molybdate, to partially saturate the conjugated aromatic ring
structure, which is represented by dihydrophenanthrene. The hydrogen donor solvent
or diluent is mixed with the residual oil and fed to a resid hydrocracker upgrader.
Hydrogen radicals (H) are produced by the hydrogen donor solvent or diluent to decrease
the polymerization rate of the cracked products. Then, the spent hydrogen donor solvent
is recovered

by distillation and deasphalting and is recycled to the hydrotreating step. The prior
art exclusively uses distillation or the combination of reaction and distillation
to produce a distillate process derived hydrogen donor diluent precursor. This invention
uses solvent deasphalting to produce a non-distillable resin hydrogen donor solvent
precursor.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The method according to he invention will now be described by way of example with
reference to the accompanying Figure, which is a schematic flow diagram of a plant
for performing the method according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] With reference to the Figure, a resid feed stream 1 is sent to a resid hydrocracker
upgrader 2. The preferred operating conditions are highly dependent on the properties
of the resid feed 1. The residual oil feed may be derived from a wide variety of hydrocarbon
sources, e.g., petroleum oil, bitumen, coal derived liquids, or biomass. Distillates
are preferably removed from the hydrocarbon resid source by conventional vacuum distillation.
Preferably 95% of the components in the resid feed by weight have normal boiling points
greater than 450°C, more preferably greater than 480°C, and more preferably about
520°C. Typically, an appropriate resid feed has a Conradson Carbon content greater
than 10 weight %, a sulfur content in the order of or greater than 1 weight % sulfur,
a vanadium and nickel content greater than 100 ppm, a heptane insoluble fraction greater
than about 5 weight %, and a hydrogen to carbon atomic ratio of less than about 1.2
1, and a density greater than about 1.0 gm/cm
3.
[0015] The resid hydrocracker upgrader 2 converts the resid feed 1, recycle donor solvent
feed 3 from a resid hydrotreater 14, and optional oil product feed 5 from a deasphalter
6 to a petroleum distillates product which is taken through line 7 and a cracked resid
stream which flows into line 8. The resid hydrocracker upgrader 2 typically consists
of a conventional ebullated bed hydrocracker (see
U.S. Patent 4,686,028 for process details), an atmospheric distillation column, and a vacuum distillation
column.
[0016] The ebullated bed hydrocracker (resid hydrocracker upgrader 2) typically operates
in a hydrogen partial pressure range between 50 and 210 bar and typically about 140
bar, a temperature range of 410 to 530°C and typically about 470°C, and a hydrogen
donor solvent to resid feed weight ratio range of 0.1:1 to 1:1. The liquid reactant
residence time is adjusted to provide a resid-to-distillate conversion between 30%
and 90% and typically about 70%. The ebullated bed hydrocracker typically uses a conventional
cobalt-molybdenum, nickel-molybdenum or nickel-cobalt-molybdenum on alumina catalyst
in a spherical or extrudate form with a means to periodically replace a portion of
the catalyst inventory with fresh catalyst during normal operations. In addition,
a conventional colloidal molybdenum sulfide catalyst may be advantageously used. The
preferred ebullated bed hydrocracker operating conditions are highly dependent on
the source of the resid feed 1 and are best determined based on pilot plant tests.
An ebullated bed hydrocracker typically operates with a temperature between 415 and
450°C, a hydrogen partial pressure 140 and 210 bar, a ratio of the hourly resid volumetric
feed rate to reactor volume between 0.25:1 and 5:1, and a cobalt-molybdate or nickel-molybdate
catalyst bed at between 5 and 30% volume expansion. The cracked resid product in line
8 is typically produced by first removing gas and distillate components in a distillation
column operating at a pressure slightly greater than atmospheric pressure and then
removing a majority of the remaining distillate components in a vacuum distillation
to produce the upgraded distillate oil product stream that flows to line 7 and the
cracked resid feed that flows via line 8 to deasphalter 6.
[0017] The methods for the production of asphaltene, resin, and deasphalted oil products
in a deasphalter are well established (
U.S. Patents 4,686,028;
4,715,946;
4,810,367;
5,228,978;
5,914,010;
5,919,355; and
6,106,701). The deasphalting process separates species in residual oil based on their solubility
in paraffinic solvents. The effectiveness of the solvent in line 9 can be adjusted
by either selecting the number of carbon atoms in the paraffinic solvent (usually
between 3 and 5 carbons) or adjusting the solvent's temperature in relation to its
critical temperature, or both.
Any number of deasphalter products can theoretically be produced by progressively
decreasing the solvent's effectiveness and removing the separated phase. Both the
deasphalter unit operation and laboratory heavy oil analytical methods use the sequential
elution fractionation to separate heavy oil into fractions for analysis and products.
See, for example,
Klaus H. Altgelt and Mieczyslaw M. Boduszynski, "Composition and analysis of heavy
petroleum fractions," Marcel Dekker, 1994, ISBN 0-8247-84946-6, page 63. A typical deasphalter unit is generally designed to produce two or three products.
A two product deasphalter produces an asphaltene stream and deasphalted oil stream
with the asphaltene stream having the lower solubility in the solvent. A three product
deasphalter additionally produces a resin product with intermediate solubility between
the oil and asphaltene products.
[0018] The deasphalter operating conditions are adjusted to provide the desired asphaltene,
resin, and oil properties. In the present invention, the asphaltene product yield
should be minimized with the constraint that the asphaltene product passing through
line 10 can be handled by the downstream processing unit, e.g., an asphaltene gasifier
12 in the Figure. Oxygen is fed to the asphaltene gasifier 12 through line 15. Once
the minimum practical asphaltene yield has been determined, a reasonable resin yield
can be estimated based on the resin hydrogen to carbon ratio as a function of the
resin yield. Analysis of laboratory scale sequential elution fractionations can be
used to determine the effect of oil, resin, and asphaltene weight fraction yield on
the oil, resin, and asphaltene product stream properties. The hydrogen donor solvent
precursor should have a hydrogen to carbon atomic ratio that is preferably less than
1.5:1, more preferably less than 1.3:1, and most preferably less than 1.2:1. The deasphalter
oil product in line 5 contains essentially the components in deasphalter feed 8 that
do not enter either the asphaltene or resin products, which are fed to the asphaltene
gasifier 12 and resid hydrotreater 11, respectively. The deasphalter oil product in
line 5 may be recycled to the ebullated bed resid hydrocracker 2.
[0019] However, this deasphalter oil product is a poor ebullated bed resid hydrocracker
feedstock because it has a lower cracking rate than either resin or asphaltenes and
is also is a relatively poor solvent for coke precursors. This material is therefore
preferably fed to a fluid catalytic cracker or coker (not shown).
[0020] The resin product of the solvent deasphalter that is sent to line 11 and a flow of
hydrogen in line 13 are fed to a resid hydrotreater 14. The resid hydrotreater 14
may be a conventional trickle-bed, down-flow, ebullated bed, or entrained flow resid
hydrotreating reactor. The trickle-bed and ebullated bed reactors would typically
use a nickel-molybdenum on alumina catalyst with sufficient pore diameter to allow
ready access of the resin feedstock. The entrained flow reactor would typically use
a colloidal molybdenum sulfide catalyst. The ebullated bed reactor could also use
a colloidal molybdenum sulfide catalyst in addition to the supported catalyst. The
molecular hydrogen feed is generally between 250 and 500 Nm
3 H
2/m
3 resin, and is fed to resid hydrotreater 14 via line 13. The resid hydrotreater 14
operating pressure is preferably greater than the ebullated bed resid hydrocracker
upgrader 2 operating pressure to allow the hydrogen donor solvent and unreacted hydrogen
to flow to the ebullated bed resid hydrocracker via line 3. The resid hydrotreater
14 generally operates in the range of about 370° to 430°C, significantly lower than
the 410° to 530° C typical operating temperature range for the ebullated bed resid
hydrocracker. The resid hydrotreater 14 has a catalyst bed volume that is adjusted
such that the hydrogen consumption is between 100 and 200 Nm
3 H
2/m
3 resin.
[0021] The method according to the invention offers a number of advantages relative to earlier
processes. First, the resid hydrotreater is much more efficient than the ebullated
bed resid hydrocracker because the catalyst deactivation rate due to metals and carbon
deposition is much lower. The resid hydrotreater can operate at the optimum temperature
for hydrogenation.
[0022] Second, the hydrogen donor solvent significantly improves the performance of the
ebullated bed resid hydrocracker. The maximum operable resid conversion in an ebullated
bed resid hydrocracker tends to decrease with increasing reactor operating temperature,
e.g., see
U.S. Patent 4,427,535. Therefore, there is a decrease in reactor operability associated with an increase
in the resid cracking rate. With hydrogen donor solvents and diluents, the hydrogen
use efficiency and maximum operable resid conversion increases with increasing temperature
e.g. see U.S Patents 4,698,147 and 4,002,556. The major advantage of a process derived
resin hydrogen donor solvent relative to distillate hydrogen donor diluent is that
a process derived resin hydrogen donor solvent provides the opportunity to significantly
increase resid hydrocracker operability at high temperature without diluting the resid
reactant with a distillate hydrogen donor diluent.
[0023] Since asphaltenes in line 10 are not stable, it is desirable to promptly and usefully
dispose of this troublesome material. Conventional pitch gasification for hydrogen
production (see
U.S. Patents 4,115,246 and
5,958,365 and
Gasification by Christopher Higman and Maarten van der Bugrt-SBN 0-7506-7707-4) is the preferred asphaltene disposal method. The raw gas leaves the asphaltene gasifier
through line 16 and enters the hydrogen production and purification unit 17. Hydrogen
from the hydrogen production and purification unit leaves through line 18 where it
may optionally connected with a supplemental hydrogen source 20 and is available for
use in the resid hydrotreater 14 through line 13 and the resid hydrocracker 2 through
line 4. Waste gas from the hydrogen production and purification unit 17 leaves through
line 19 where it can be disposed of or employed in an appropriate manner.
[0024] While this invention has been described with respect to particular embodiments thereof,
it is apparent that numerous other forms and modifications of the invention will be
obvious to those skilled in the art. The appending claims in this invention generally
should be construed to cover all such obvious forms and modifications which are within
the true spirit and scope of the present invention.
1. A method for increasing the maximum resid conversion and resid conversion rate in
a resid hydrocracker upgrader comprising the steps:
a) producing a hydrogen donor solvent precursor in said resid hydrocracker, wherein
said precursor is produced by hydroreforming reactions of a hydrogen donor solvent
feed;
b) directing said hydrogen donor solvent precursor to a solvent deasphalting unit,
wherein a resin stream containing said hydrogen donor solvent precursor is formed;
c) directing said resin stream to a resid hydrotreater unit, wherein hydrogen donor
solvent is regenerated; and
d) directing said hydrogen donor solvent to said resid hydrocracker upgrader.
2. A method as claimed in claim 1, wherein said hydrogen donor solvent precursor is produced
by hydrocracking of the resid feed.
3. A method as claimed in claim 1 or claim 2, wherein said resid hydrocracker upgrader
comprises an ebullated bed hydrocracker, atmospheric pressure distillation column
and vacuum distillation column.
4. A method as claimed in claim 3, wherein said ebullated bed hydrocracker operates at
a hydrogen partial pressure of 50 to 210 bar and at a temperature of about 410 °C
to 530 °C.
5. A method as claimed in claim 3 or claim 4, wherein the hydrogen donor solvent to resid
feed weight ratio range is about 0.1 to 1 in said ebullated bed hydrocracker.
6. A method as claimed in any one of claims 3 to 5, wherein said ebullated bed hydrocracker
contains a catalyst selected from the group consisting of cobalt-molybdenum, nickel-molybdenum
and nickel-cobalt-molybdenum on alumina catalyst.
7. A method as claimed in any one of the preceding claims, wherein the resid hydrocracker
has a feed of residual oil selected from the group consisting of petroleum oil, bitumen,
coal derived liquids, and biomass.
8. A method as claimed in any one of the preceding claims, wherein said hydrogen donor
solvent precursor has a hydrogen to carbon ratio of less than about 1.5 to 1.
9. A method as claimed in any one of the preceding claims, wherein said resid hydrotreater
is a down-flow, trickle-flow, ebullated bed, or entrained flow reactor.
10. A method as claimed in claim 9, wherein the molecular hydrogen feed rate to the hydrotreater
is between 250 and 500 Nm3 hydrogen per m3 resin.
11. A method of operating a resid hydrocracker upgrader comprising the steps:
a) producing a hydrogen donor solvent precursor in said resid hydrocracker upgrader,
wherein said precursor is produced by hydroreforming reactions of a hydrogen donor
solvent feed;
b) directing said hydrogen donor solvent precursor to a solvent deasphalting unit,
wherein a resin stream containing said hydrogen donor solvent precursor is formed;
c) directing said resin stream to a resid hydrotreater unit, wherein hydrogen donor
solvent is regenerated; and
d) directing said regenerated hydrogen donor solvent to said resid hydrocracker upgrader
as hydrogen donor solvent feed.